Influence of Different Process Variables in the Final Characteristics of an Oil in Water Cosmetic Emulsion: A Scale-up Strategy

Global cosmetics market has been steadily growing during last years. A major driver of this, is the consumer need for innovative products with multifunctional attributes. As the market is highly competitive, there is need to reduce the launch time of products, thus becoming in a dominant constrain during product design.

Despite different tools have been developed for in-silico product conception and design, a limiting factor still remains in the scale-up process. In particular, when developing structured products in the cosmetics industry, it is necessary to consider several variables to ensure that the product will fulfill the desired properties and attributes, but also will maintain a long-term stability. Variables such as stirring rates, equipment geometry, emulsification temperature, mixing times, heating or cooling rates, and ingredients addition procedures play a major impact in the final characteristics of the emulsified products. Some of these variables need to be adjusted to account for the change in the mixing-volume-to-transfer-area ratio. Currently, the scale-up to industrial production is a time-consuming, resources-intensive process, traditionally involving trial and error techniques.

In this regard, different systematic scale-up techniques have been developed for the production of emulsion. Specifically, the use of process invariants such as dimensionless numbers of the form ND^α, have been integrated as key parameters during change of scale. While these techniques mainly focus in maintaining a defined drop size distribution, it has been verified that this doesn’t guarantee to maintain all the characteristics of the emulsion.

Thus, the aim of this work is to study the influence of some process variables, focusing in the change on the heat transfer conditions during scale-up, and their impact in the characteristics of an oil in water emulsion. The study was carried by the manufacture of a cosmetic emulsion at three different processing scales in order to identify suitable scale-up strategies.